1. Field of the Invention
The present invention relates to a lens driving apparatus for use in a camera equipped with an auto-focusing function and a camera-shake correction function, a camera module, and a camera-equipped mobile terminal.
2. Description of Related Art
Conventionally, as a camera installed in a mobile terminal such as a smartphone, a camera equipped with an auto-focusing function and a camera-shake correction function is known. Such a camera adopts a lens driving apparatus that automatically focuses on a subject to be captured by moving a lens barrel and can reduce an image defect by correcting a camera-shake (vibration) when capturing an image (for example, WO2011/021559).
A lens driving apparatus disclosed in WO2011/021559 includes a lens holder moving section that supports a lens holder in which a lens barrel is fixed, wherein the lens holder is supported in such a manner as to be movable in the optical axis direction. In this lens driving apparatus, an auto-focusing first coil is disposed around the lens barrel (lens holder), and a permanent magnet is disposed to the lens holder moving section, whereby an auto-focusing lens driving section (hereinafter referred to as AF lens driving section) is configured. The AF lens driving section moves the lens holder in the optical axis direction by utilizing an electromagnetic force (Lorentz force) which acts on a first coil when a current is passed through the first coil, to thereby perform auto-focusing.
In addition, in the lens driving apparatus disclosed in WO2011/021559, a second coil is disposed in a spaced relationship with an auto-focusing permanent magnet in the optical axis direction, whereby a camera-shake correction lens driving section is configured. The camera-shake correction lens driving section moves the lens holder moving section and the lens holder along a plane orthogonal to the optical axis direction by utilizing an electromagnetic force which is generated when a current is passed through the second coil, to thereby perform camera-shake correction.
The portion at which the second coil is disposed is referred to as a fixed section since the portion does not move at the time of the camera-shake correction, whereas the lens holder and the lens holder moving section are referred to as a movable section since they rock at the time of the camera-shake correction. The movable section is supported to the fixed section by a supporting member such as a suspension wire for example so as to be able to rock.
In the above-mentioned manner, the AF lens driving section and the camera-shake correction lens driving section share the permanent magnet, whereby the size and thickness of the lens driving apparatus can be reduced.
Generally, a lens holder moving section has an external form which is square in plan view as viewed in the optical axis direction, and includes a substantially circular (which encompasses regular polygons) holder housing section which is formed at a center portion and configured to house a lens holder. A permanent magnet for auto-focusing and camera-shake correction is composed of a cuboid bar magnet, and disposed along the four sides defining the external shape of the lens holder moving section. That is, the permanent magnet is disposed in parallel with the outer periphery of the product. In addition, the second coil making up the camera-shake correction lens driving section has an ellipsoidal form with rounded corners matching the form of the permanent magnet. The second coil is also disposed in parallel with the outer periphery of the product.
As used herein, the term “plan view” means a plan view in the optical axis direction.
In recent years, because of a trend toward multi-functionality of mobile terminals and the advent of thin devices such as smartphones, there has been a growing demand for further reduction in size and thickness. However, it is difficult to achieve further size reduction with the configuration of the conventional lens driving apparatuses.
More specifically, the conventional lens driving apparatus requires a sufficient space for disposing the permanent magnet in parallel with the outer periphery of the product around the holder housing section of the lens holder moving section. In addition, the external size of the fixed section at which the second coil is disposed is substantially the same as the lens holder moving section, which also hinders miniaturization.